Gate electrode having a capping layer

ABSTRACT

A method of manufacturing a semiconductor device and a novel semiconductor device are disclosed herein. An exemplary method includes sputtering a capping layer in-situ on a gate dielectric layer, before any high temperature processing steps are performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/770,767, filed Feb. 19, 2013, which is a continuation of U.S. patentapplication Ser. No. 13/044,356, filed Mar. 9, 2011, now U.S. Pat. No.8,390,082, issued Mar. 5, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/354,702, filed Jan. 15, 2009, now U.S. Pat. No.7,915,694, issued Mar. 29, 2011, which is a divisional of U.S. patentapplication Ser. No. 11/322,745, filed Dec. 30, 2005, now U.S. Pat. No.7,524,727, issued Apr. 28, 2009, the entire contents of which are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor structures andmanufacturing. In particular, the present invention relates to themanufacturing of high dielectric constant gate stacks.

BACKGROUND OF THE INVENTION

Advances in semiconductor manufacturing technology have led to theintegration of billions of circuit elements, such as transistors, on asingle integrated circuit (IC). In order to integrate increasing numbersof circuit elements onto an integrated circuit it has been necessary toreduce the dimensions of the electronic devices (i.e., ametal-oxide-semiconductor (MOS) transistor).

This scaling down involves making all of the layers in the electronicdevices as thin as possible. Silicon dioxide has been the preferred gatedielectric material; however, additional thinning of silicon dioxidecompromises the performance and functionality of the electronic devices(e.g., lost function due to charge leakage). One practice has been tosubstitute the silicon dioxide layer with a higher permittivity gatedielectric since a high permittivity layer can be made thicker and stillmaintain a high capacitance characteristic. The materials used to formthe high permittivity gate dielectric are referred to as high dielectricconstant (high-k) dielectric materials.

Most high-k gate dielectric materials however, are not compatible withcrystalline silicon or polycrystalline silicon (polysilicon) gateelectrodes. In order to switch to the high-k gate dielectric, manymanufacturers have replaced the conventional polysilicon gate electrodewith a metal gate electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is an end cross-sectional view illustrating a semiconductorstructure after formation of a dielectric layer on a substrate accordingto an embodiment of the invention;

FIG. 2 is an end cross-sectional view further illustrating asemiconductor structure after formation of a barrier layer on thedielectric layer according to an embodiment of the invention;

FIG. 3 is an end cross-sectional view further illustrating asemiconductor structure after sputtering a capping layer on the barrierlayer according to an embodiment of the invention;

FIG. 3A is a schematic view illustrating a cluster tool for making asemiconductor structure without exposure to oxygen;

FIG. 4 is an end cross-sectional view illustrating a semiconductorstructure after formation a polysilicon layer on the capping layeraccording to an embodiment of the invention;

FIG. 5 is an end cross-sectional view illustrating a semiconductorstructure after ion implantation of the substrate according to anembodiment of the invention;

FIG. 6 is an end cross-sectional view illustrating a semiconductorstructure after formation of spacers on the substrate according to anembodiment of the invention;

FIG. 7 is an end cross-sectional view illustrating a semiconductorstructure after formation of an interlayer dielectric on the substrateaccording to an embodiment of the invention;

FIG. 8 is an end cross-sectional view illustrating a semiconductorstructure after removal of the polysilicon layer, capping layer andbarrier layer according to an embodiment of the invention;

FIG. 9 is an end cross-sectional view illustrating a semiconductorstructure after deposition of a metal gate electrode on the dielectriclayer according to an embodiment of the invention;

FIG. 10 is an end cross-sectional view of a CMOS transistor; and

FIG. 11 is a perspective view of a tri-gate transistor.

DETAILED DESCRIPTION

A method, which includes depositing a dielectric layer on a substrate,followed by deposition of a capping layer in-situ over the dielectriclayer prior to any high temperature processing, is disclosed herein. Thecapping layer acts as an oxygen diffusion barrier or seal to preventexposure of the dielectric layer to oxygen. An optionally sacrificialbarrier layer may be deposited between the dielectric layer and thecapping layer. Each of the dielectric layer, barrier layer and cappinglayer are desirably formed in situ and without exposing the layers tooxygen.

In one embodiment, when the dielectric layer is formed on the substrate,the dielectric layer is a kinetic product. That is, the dielectric layeris formed using a low energy (e.g., low temperature) process. A cappinglayer is then formed on the kinetic product dielectric layer to seal thedielectric layer until a subsequent high energy process occurs. A highenergy (e.g., high temperature) process, such as, for example,annealing, results in a transformation of the dielectric layer from akinetic product to a thermodynamic product (i.e., more thermodynamicallystable). After the transformation, a replacement gate process may besubsequently performed, because the stack can be exposed to oxygenwithout risking the disadvantageous effects of oxygen exposure.Deposition of a metal gate electrode over the dielectric layer mayfollow the removal process.

As shown in FIG. 1 of the accompanying drawings, the process begins byproviding a substrate 10. Any well-known substrate, such as, but notlimited to, a monocrystalline silicon may be used. In one embodiment,the substrate 10 is a silicon wafer. The substrate 10 may be formed fromother materials, such as, but not limited to, germanium, indiumantimonide, lead telluride, indium arsenide, indium phosphide, galliumarsenide, gallium antimonide and the like. The substrate 10 may be asilicon-on-insulator structure.

With reference back to FIG. 1, the process continues by depositing adielectric layer 12 on the substrate 10. In one embodiment, thedielectric layer 12 is a gate dielectric layer.

The dielectric layer 12 is desirably made of a high-k material; that is,the high-k dielectric layer 12 is made of a material having a dielectricconstant (k) greater than that of silicon dioxide (e.g., ˜4). Some ofthe materials that may be used to make the high-k gate dielectric layer12 include, but are not limited to: hafnium oxide, lanthanum oxide,zirconium oxide, zirconium silicon oxide, titanium oxide, tantalumoxide, barium strontium titanium oxide, barium titanium oxide, strontiumtitanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalumoxide, lead zinc niobate, and the like.

In one embodiment, the dielectric layer 12 is sufficiently thick toelectrically isolate the substrate from a subsequently formed gateelectrode. In one embodiment, the thickness of the dielectric layer 12is about 5-25 angstroms.

The dielectric layer 12 may be formed on substrate 10 using any suitabletechnique including, but not limited to, atomic layer deposition (ALD),thermal oxidation, chemical vapor deposition (CVD) and physical vapordeposition (PVD) processes. In one embodiment, the dielectric layer isformed by an ALD process. In the ALD process, the dielectric layer 12 isformed by exposing the substrate to alternating metal-containingprecursors and oxygen-containing precursors until a layer having thedesired thickness has been formed. Exemplary metal precursors includehalfnium tetrachloride and lanthanum trichloride. An exemplaryoxygen-containing precursor is water. In another embodiment, thedielectric layer 12 is formed by depositing a metal layer on thesubstrate and then thermally oxidizing the metal layer.

In one embodiment, the process used to form the dielectric layer 12results in a dielectric layer 12 being formed as a kinetic product. Whenthe dielectric layer 12 is a kinetic product, the dielectric layermaterial may have vacant sites. If the dielectric layer 12 is exposed tooxygen, oxygen may pass through the vacant sites to form an interfacialsilicon oxide layer at the interface of the dielectric layer 12 and thesubstrate 10, which can lead to an increase in the equivalent oxidethickness (EOT) of the gate dielectric layer. When the dielectric layer12 is a kinetic product, it is also less stable. However, the processeswhich result in a kinetic product also allow for greater accuracy andproduce a dielectric layer 12 that is thin and uniform.

In some embodiments, the process continues by forming an optionalbarrier layer 14 on the dielectric layer 12, as shown in FIG. 2. Thebarrier layer 14 prevents interaction of a subsequently formed cappinglayer (see FIG. 3) with the dielectric layer 12.

Accordingly, in one embodiment, the barrier layer 14 is sufficientlythick to isolate the dielectric layer 12 from the subsequently formedcapping layer (see FIG. 3). The thickness of the barrier layer 14 istypically less than 25 angstroms, and more typically 10-20 angstroms.

In one embodiment, the barrier layer 14 and the dielectric layer 12 aredeposited in situ. That is, exposure of the substrate 10 to oxygenbetween formation of each layer is minimized, such as by forming and/ortransferring the layers under vacuum or inert ambient. In particular,the barrier layer 14 is formed by a process in which the dielectriclayer 12 is not exposed to oxygen. In one embodiment, the dielectriclayer 12 and barrier layer 14 are formed in the same chamber. Inaddition, the barrier layer 14 is typically deposited at a lowtemperature.

Any process suitable for depositing thin layers on a semiconductordevice, as known to those of skill of the art, may be used to form thebarrier layer 14, such as, for example, ALD, CVD, PVD (e.g., sputtering)or mechanical deposition.

The barrier layer 14 may be any suitable material that resists impuritydiffusion and forms a chemically stable interface with the dielectriclayer 12. The barrier layer 14 may be formed from a metal or adielectric material. An exemplary metal includes titanium nitride(TixNy). Exemplary dielectric materials include hafnium nitride andsilicon nitride (Si3N4).

In some embodiments of the invention, the barrier layer 14 issacrificial, in which case the barrier layer 14 is subsequently removedand does not form part of the gate stack. In this case, the barrierlayer 14 may be a dielectric layer, such as, for example, hafniumnitride (HfxNy), or a metal, such as, for example, titanium nitride(TixNy).

In other embodiments of the invention, the barrier layer 14 isnon-sacrificial, in which case the barrier layer 14 remains and formspart of the gate stack. In this case, the barrier layer 14 may be ametal, such as, for example, titanium nitride (TixNy).

In embodiments in which the barrier layer 14 is non-sacrificial andformed from a metal, the barrier layer 14 is formed sufficiently thin soas to be transparent to the work function (WF) controlling metal ormetals of the gate electrode. In one embodiment, the barrier layer 14 isformed to a thickness less than 25 angstroms.

In one specific embodiment, the dielectric layer 12 is HfO2 and isformed on the substrate using an ALD process, and the barrier layer 14is TixNy and is in situ sputter deposited on the dielectric layer 12.

As shown in FIG. 3, the process continues by forming a capping layer 16on the barrier layer 14. The capping layer 16 is typically a conformalfilm.

The function of the capping layer 16 is to seal the dielectric layer 12from oxygen and other impurities, which can flow through the dielectriclayer 12 to cause oxide growth on the underlying substrate or otherwisealter the quality of the dielectric layer 12. It may be particularlydesirable to seal the dielectric layer 12 when it is a kinetic product.The capping layer 16 prevents nitridization and oxidation of thedielectric layer 12 that may occur during later processing steps. In oneembodiment, the capping layer 16 desirably seals the dielectric layer 12and optional barrier layer 14 until the dielectric layer 12 is convertedfrom a kinetic product into a thermodynamically stable product.

In one embodiment, the capping layer 16 is formed “in situ” with thedielectric layer 12 and, if used, the barrier layer 14. The cappinglayer 16 is formed on the optional barrier layer 14 and dielectric layer12 using a process in which the dielectric layer 12 is not exposed tooxygen. Although the process may be performed under vacuum, otherprocesses which minimize oxygen availability may be used. In oneembodiment, the capping layer 16 is sputter deposited on the dielectriclayer 12.

In one embodiment, the capping layer 16 is sufficiently thick to preventoxygen from passing through to the barrier layer 14 and dielectric layer12. In some embodiments, the thickness of the capping layer 16 is atleast 200 angstroms.

The capping layer 16 is ideally formed at a low temperature using one ofthe previously described processes for depositing thin layers, such as,for example, sputtering to prevent incorporation of impurities into thedielectric layer 12. In one embodiment, the formation of the cappinglayer 16 is at a low temperature. In one embodiment, the capping layer16 is formed at a temperature that is less than about 350° C.

In one embodiment, the capping layer 16 is formed from a material thatcan be selectively removed in a subsequent replacement gate process. Inone embodiment, the capping layer 16 is a material that increaseshardening of the dielectric layer 12. In one embodiment, the cappinglayer 16 is a material that can withstand subsequent processing stepswhich occur at temperatures greater than about 1200° C.

In one embodiment, the capping layer 16 is silicon. Other exemplarycapping layer materials include germanium, silicon germanium, siliconnitride, and the like.

In a specific embodiment of the present invention, the capping layer 16is an in situ sputter deposited amorphous silicon film. An amorphoussilicon film contains random grain boundaries which prevent channelingof oxygen through the dielectric layer 12.

In one specific embodiment, the dielectric layer 12 is HfO2 and isformed on the substrate using an ALD process, and the optional barrierlayer 14 is TixNy and is in situ sputter deposited on the dielectriclayer. In one specific embodiment, the capping layer 16 is silicon andis in situ sputter deposited at room temperature.

As discussed above, the layers 12-16 may be formed in situ. In oneembodiment, a cluster tool, such as the cluster tool shown in FIG. 3A,may be used to accomplish in situ deposition of layers 12-16. Theprocesses for forming each of the layers 12-16 may be done in the samechamber or a different chamber than each of the other processes.

FIG. 3A shows a cluster tool 100, which, in one embodiment, may be usedto complete the depositions in situ. The cluster tool 100 includes aFront Opening Unified Pod (FOUP) 102, a transfer chamber 104, adielectric layer deposition chamber 106, a barrier layer depositionchamber 108, a capping layer deposition chamber 110 and a computer 112.The transfer chamber 104 may include a robot 114 therein.

The transfer chamber 104 is desirably vacated or has an inert ambient.The transfer chamber 104 is centrally located, such that each of theFOUP 102 and chambers 106, 108 and 110 are branches off of the transferchamber 104. The robot 114 allows the wafer to be transferred among eachof the chambers 104-110. The dielectric layer deposition chamber 106 maybe an ALD chamber. The deposition chamber 108 may be a sputter chamber.The capping layer deposition chamber 110 may also be a sputter chamber.

In use, the computer 112 controls the movement of the semiconductorwafer among each of the chambers 102-110 via robot 114. The computer 112also controls the submodules (the processes) associated with each of thechambers. As a result, a substrate can be transferred between each ofthe chambers 106, 108 and 110, respectively, through the transferchamber 104, without breaking the vacuum (i.e., without exposing thelayers to oxygen) to form the stack shown in FIG. 3.

In one embodiment, the process begins by placing a silicon wafer in theFOUP 102. The silicon wafer then passes through the transfer chamber104, which is under vacuum and/or in an inert ambient. The wafer passesfrom the transfer chamber 104 and into the dielectric layer depositionchamber 106, where a dielectric layer 12, such as HfO2, is formed on thesubstrate using an ALD process. The wafer then passes through thetransfer chamber 104, and into the barrier layer deposition chamber 108,where a barrier layer 14, such as TixNy, is sputter deposited on thedielectric layer. The wafer then passes through the transfer chamber 104and into the capping layer deposition chamber 110, where a capping layer16, such as silicon, is deposited at room temperature under vacuum usinga PVD process. The capping layer 16 seals the dielectric layer 12 andoptional barrier layer 14, so no interstitial oxide layer is formed atthe interface of the substrate and dielectric layer.

The process may continue by depositing a masking layer 18 on the cappinglayer 16, as shown in FIG. 4. The layers 12-18 together form a stack offilms 118.

The masking layer 18 acts as a mask during an ion implantation processwhich follows deposition of the masking layer 18. In one embodiment, themasking layer 18 is formed from polysilicon.

In one embodiment, the masking layer 18 is sufficiently thick for ionimplantation (See FIG. 5). In one embodiment, the masking layer 18 issufficiently thick to mask an underlying channel region (see FIG. 5).

The masking layer 18 is deposited using any well known process, such as,for example, CVD. In one embodiment, the masking layer 18 is depositedusing a CVD process in a CVD chamber. In one embodiment, the CVD chamberis part of the cluster tool, described above with reference to FIG. 3A.

Alternatively, the masking layer 18 may be deposited outside of thevacuum. It is to be appreciated that because the capping layer 16 hasbeen deposited and acts as an oxygen seal, the masking layer 18 does notneed to be deposited in situ.

In one embodiment, the masking layer 18 is a sacrificial gate electrode.That is, the masking layer 18 will be removed in a subsequentreplacement gate process (See FIG. 8).

Next, the masking layer 18 is patterned with, for example, well knownphotolithography and etching steps. In one embodiment, all of the layers(i.e., dielectric layer 12, barrier layer 14, capping layer 16, andmasking layer 18) are patterned.

The process continues, as shown in FIG. 5, by implanting the substrate10 with ions to form source/drain extensions 19. A channel region isthereby formed between the source/drain extensions 19 and under thedielectric layer 12.

As shown in FIG. 6, the process may continue by depositing spacers 20.Spacers 20 seal the sides of the structure, and encapsulate thedielectric layer 12.

The spacers 20 are typically made of nitride or oxide. Exemplary spacermaterials include, but are not limited to, silicon nitride, carbon dopednitride, or carbon doped nitride without oxide components.

In one embodiment, the spacers 20 are formed by a CVD process. Thespacer depositions process occurs, in one embodiment, at a relativelyhigh temperature of approximately 500° C. The temperature (greater than350° C.) is acceptable because the top surface of the dielectric layer12 is sealed by the capping layer 16 and the dielectric layer 12 istherefore not exposed or only the edge of the layer is exposed.

In one embodiment, a high temperature step follows spacer deposition,which anneals the dielectric layer 12 and activates the implanteddopants. In one embodiment, the high temperature step is a source drainanneal (SDAL). In one embodiment, the high temperature step is a rapidthermal anneal (RTA).

In one embodiment, silicide is formed during the high temperature step.In particular, in one embodiment, self-aligned silicide (SALICIDE) maybe formed during the high temperature step. The silicide may be used toform low-resistance contacts.

During high temperature processes, the dielectric layer 12 maytransition from its deposited kinetic product state to a thermodynamicproduct state. The transition from a kinetic product to a thermodynamicproduct may cause unsaturated sites in the dielectric layer 13 to becomesaturated. The resulting thermodynamic dielectric layer 13 is typicallymore stable and consistent than the kinetic dielectric layer 12.

In one embodiment, the dielectric layer 12 remains sealed with thecapping layer 16 until the dielectric layer has transformed from thekinetic product state (12) into its thermodynamically stable state (13)while other processing is done.

It is believed that, during the sputtering process, the capping layermaterial may enter the lattice structure of the dielectric layermaterial. The high temperature processing step, such as, for example, ananneal, may harden the capping layer material in the lattice structureof the dielectric material. The vacancies in the dielectric layer 12thus may be filled with capping layer material. Alternatively, thesevacancies may at least be sealed by the capping layer 16. In oneembodiment, at least the top surface of the dielectric layer 12 ishardened as a result of the filled vacancies. The incorporation of thecapping layer material into the dielectric layer lattice structure mayprevent further diffusion of oxygen and nitrogen through the dielectriclayer 12. Thus, the gate stack has a dielectric layer 12 that is in amore stable, thermodynamic state because the dielectric layer 12 wassealed with the capping layer 16 during the high temperature processingsteps.

In one embodiment, the process ends after the high-temperatureprocessing step.

As shown in FIG. 7, in one embodiment, the process continues by formingan interlayer dielectric 22 on the substrate. The interlayer dielectric22 enables the transistor to be insulated from and connected to othertransistor structures.

The interlayer dielectric 22 is deposited using known techniques andusing known dielectric materials. The interlayer dielectric 22 may beblanket deposited over the substrate and gate structure, and thenplanarized using a chemical or mechanical polishing technique, exposingthe top surface of the polysilicon layer 18.

In some embodiments, a replacement gate process follows deposition ofthe interlayer dielectric 22. The stack of films having a thermodynamicdielectric layer 13 is particularly suitable for a replacement gateprocess because the dielectric layer is thermodynamically stable.

As shown in FIG. 8, in one embodiment, a replacement gate processfollows deposition of the interlayer dielectric 22. The replacement gateprocess begins by etching out and removing the polysilicon layer 18 andcapping layer 16. Optionally, the barrier layer 14 may also be removed.Thus, a trench 23 is formed between the spacers 20 and above thedielectric layer 13. A wet etch process using, for example, tetramethylammonium hydroxide (TMAH), may be used to remove the layers 16, 18. Itwill be appreciated by those of skill in the art that the material ofthe capping layer 16 will be different than the material of the spacers20, as the capping layer 16 is removed, while the spacers 20 remain.

The process leaves, at a minimum, the high-K dielectric layer 13. Thedielectric layer 13 that remains is an annealed, electrically thin andintact dielectric layer. The dielectric layer 13 may also be athermodynamic product.

The capping layer 16 and, optionally, the barrier layer 14 can beremoved, and the dielectric layer 13 can be exposed to the atmosphere.The dielectric layer 12 can now be exposed because the dielectric layer13 has been transformed from a kinetic product into a more stablethermodynamic product state.

Work function metal deposition may follow removal of the capping layer16 after the high-temperature steps, as shown in FIG. 9. A transistorhaving a capping layer and subsequent work function metal depositiontypically has thin Tox, correct Vth, and is more reliable.

As shown in FIG. 9, the process may continue by depositing a gateelectrode 24 on the annealed dielectric layer 13 and between the spacers20. In one embodiment, the gate electrode 24 is a metal. A single metalor multiple metals may be used. Exemplary metals include, but are notlimited to, aluminum (Al); titanium (Ti); molybdenum (Mo); tungsten (W);metal nitrides and carbides, such as, TixNy, TixCy, TaxNy, TaxCy; and,the like. In an embodiment for a PMOS transistor, a p-type metal havinga p-type work function (WF=4.9-5.3 eV) is used. In an embodiment for aNMOS transistor, a n-type metal having a n-type work function(WF=3.9-4.3 eV) is used. In another embodiment, a mid-gap metal(WF=4.3-4.9 eV) may be used.

The gate electrode 24 may be deposited using known techniques. Apolishing process, such as chemical mechanical polishing (CMP), may beperformed to planarize the surface and expose the gate electrode 24.

Thus, a gate stack having a thermodynamic product dielectric layer 13 isformed. In addition, a gate stack is formed having an ultra-thintransition oxide layer (not shown) or no transition oxide layer. In oneembodiment, the ultra-thin transition oxide layer is a monolayer.

Transition layer oxide growth is minimized, or even eliminated, with thein-situ deposition of each of the dielectric layer 12, the barrier layer14 and the capping layer 16. Transition layer oxide growth is alsominimized, or even eliminated, with the deposition of each of thedielectric layer 12, barrier layer 14 and the capping layer 16 at a lowtemperature. A thinner transition oxide layer results in improvedtransistor performance and enables gate scaling. In addition, thetransformation of the dielectric layer 12 from a kinetic product to athermodynamic product results in a more reliable gate stack.

FIG. 10 is an end cross-sectional view of a conventional complementarymetal oxide semiconductor (CMOS) circuit 30, manufactured using themethod described in FIGS. 1-9, according to an embodiment of theinvention.

The circuit 30 includes a substrate 10, a high-k dielectric layer 12, agate electrode 24, spacers 20, source region 32 and drain region 34, anda channel region 36.

The dielectric layer 12 is formed on the substrate 10. The gateelectrode 24 is formed on the dielectric layer 12. The source and drainregions 32, 34 are formed in the substrate 10 on opposite sides of thegate electrode 24. The spacers 20 are provided on opposite sides of thegate electrode 24 and the dielectric layer 12, and over the source anddrain regions 32, 34. The gate electrode 24 may be a p-type, n-type ormid-gap metal.

An ultra-thin transition oxide layer (not shown) may be present betweenthe substrate 10 and dielectric layer 12. The dielectric layer 12 may bea thermodynamic product.

A CMOS circuit includes two transistors 30 (one PMOS transistor and oneNMOS transistor), the gates of which are connected to a voltage source.A voltage is applied to the source region 32 of each transistor 30,causing current to flow through the channel region 36 to the drainregion 34. A voltage is also applied to the gate electrode 24 of eachtransistor 30, which interferes with the current flowing in the channelregion 36 of each transistor 30. The voltage connected to the gateelectrode 24 switches the current on and off in the channel region 36 ofeach transistor, such that either the PMOS or NMOS is switched on (i.e.,current flows through the channel region 36 of only one transistor) atany given time. In NMOS devices, the signal carriers, or electrons, havea negative charge. Current is on when a NMOS transistor gate is at highvoltage, and off when its gate is at low voltage. In PMOS devices, thesignal carriers are “holes,” or an absence of electrons. The current ina PMOS transistor flows opposite that of an NMOS transistor: it is offwhen its gate voltage is high and on when its gate voltage is low.

FIG. 11 is a perspective view of a tri-gate metal oxide semiconductortransistor 40, manufactured using the method described in FIGS. 1-9,according to an embodiment of the invention.

The transistor 40 includes a substrate 10, a semiconductor body 42, agate dielectric layer 12, a gate electrode 24, a source region 32, adrain region 34 and a channel region 36. The substrate 10 includes alower monocrystalline substrate 44 and an insulating layer 46. Thesemiconductor body 42 includes a pair of laterally opposite sidewalls 48and 50 separated by a distance which defines a semiconductor body width52, and a top surface 54 and a bottom surface 56 separated by a distancewhich defines a semiconductor body height 58. The gate electrode 24 hasa pair of laterally opposite sidewalls 60 and 62 separated by a distancewhich defines the gate length 64 of the transistor 40.

The substrate 10 can be an insulating substrate or a semiconductorsubstrate. The dielectric layer 12 is formed on the top surface 54 andsidewalls 48, 50 of the semiconductor body 42. The gate electrode 24 isformed on the dielectric layer 12 on the top surface 54 of thesemiconductor body 42 and is formed adjacent to the gate dielectriclayer 12 formed on the sidewalls 48, 50 of the semiconductor body 32.The source and drain regions 32, 34 are formed in the semiconductor body42 on opposite sides of the gate electrode 24. The gate electrode 24 maybe a p-type, n-type or mid-gap metal.

Because the gate electrode 24 and the gate dielectric layer 12 surroundthe semiconductor body 42 on three sides, the transistor essentially hasthree separate channels and gates (g1, g2, g3). The gate “width” of atransistor is equal to the sum of each of the three sides of thesemiconductor body. Larger “width” transistors can be formed byconnecting several tri-gate transistors together.

An ultra-thin transition oxide layer (not shown) may be present betweenthe substrate 10 and dielectric layer 12. The dielectric layer 12 may bea thermodynamic product.

Similar to transistor 30, the gates of transistor 40 are connected to avoltage source. A voltage is applied to the source region 32, causingcurrent to flow through the channel region 36 to the drain region 34. Avoltage is also applied to the gate electrode 24, which interferes withthe current flowing in the channel region 36. The voltage connected tothe gate electrode 24 switches the current on and off in the channelregion (g1, g2 and g3).

The methods which are described and illustrated herein are not limitedto the exact sequence of acts described, nor are they necessarilylimited to the practice of all of the acts set forth. Other sequences ofevents or acts, or less than all of the events, or simultaneousoccurrence of the events, may be utilized in practicing the embodimentsof the present invention.

The foregoing description with attached drawings is only illustrative ofpossible embodiments of the described method and should only beconstrued as such. Other persons of ordinary skill in the art willrealize that many other specific embodiments are possible that fallwithin the scope and spirit of the present idea. The scope of theinvention is indicated by the following claims rather than by theforegoing description. Any and all modifications which come within themeaning and range of equivalency of the following claims are to beconsidered within their scope.

What is claimed is:
 1. A semiconductor transistor, comprising: asubstrate; a transition oxide layer disposed on the substrate; a high-kdielectric material layer disposed on the transition oxide layer, thehigh-k dielectric material layer having a thickness approximately in therange of 5-25 Angstroms; a barrier layer disposed on the high-kdielectric material layer; a capping layer disposed on the barrier layerand comprising a material different than the barrier layer, wherein thecapping layer is formed of one material which includes germanium,silicon germanium, silicon nitride, and amorphous silicon; and a gateelectrode disposed above the capping layer and comprising a materialdifferent than the capping layer, wherein the gate electrode comprises aworkfunction controlling metal; wherein a thickness of the barrier layeris less than 25 Angstroms.
 2. The semiconductor transistor of claim 1,wherein the substrate comprises silicon.
 3. The semiconductor transistorof claim 1, wherein the high-k dielectric material comprises hafnium. 4.The semiconductor transistor of claim 1, wherein the barrier layercomprises Ti and N.
 5. The semiconductor transistor of claim 1, whereinthe gate electrode comprises Ti or Al.
 6. A semiconductor transistor,comprising: a semiconductor body formed on a substrate, thesemiconductor body having a top surface and a pair of laterally oppositesidewalls; a transition oxide layer disposed on the top surface and thesidewalls of the semiconductor body; a high-k dielectric material layerdisposed on the transition oxide layer, the high-k dielectric materiallayer having a thickness approximately in the range of 5-25 Angstroms; abarrier layer disposed on the high-k dielectric material layer; acapping layer disposed on the barrier layer and comprising a materialdifferent than the barrier layer, wherein the capping layer is formed ofone material which includes germanium, silicon germanium, siliconnitride, and amorphous silicon; and a gate electrode disposed above thecapping layer and comprising a material different than the cappinglayer, wherein the gate electrode comprises a workfunction controllingmetal; wherein a thickness of the barrier layer is less than 25Angstroms.
 7. The semiconductor transistor of claim 6, wherein thesubstrate comprises silicon.
 8. The semiconductor transistor of claim 6,wherein the high-k dielectric material comprises hafnium.
 9. Thesemiconductor transistor of claim 6, wherein the barrier layer comprisesTi and N.
 10. The semiconductor transistor of claim 6, wherein the gateelectrode comprises Ti or Al.